Most engineers at a young age are unusually self-reflective.  This is a necessary trait to be able to solve puzzles, build towers from blocks, or fix things.  The curiosity to start a problem needs to be maintained by self-reflection and patience, and to complete the task takes a strong will.

Engineers are not spectators; we have to diagnose the problem and self-reflect to create ideas to help find the solution. We actively engage projects to reveal solutions to problems or yield new ideas.  Matthew Crawford, in the terrific book Shop Class is Soulcraft, describes the difference between an expert mechanic and a procedural thinker:

"The forensic perceptual expertise of the engine builder is active in the sense that he knows what he is looking for.  But with the idiot we see the result of a premature conceit of knowledge” (Crawford 2009).

Thus knowledge itself is not what separates an engineer, or a mechanic, from an idiot.  The most important difference is the humility to recognize one’s own ignorance, combined with a good amount of skill acquisition through experience. An engineer, like a master mechanic, is self-reflective and constantly aware of the possibility of making a mistake.  Before taking a hammer to the problem, the engineer (or master mechanic) reflects and asks questions regarding the solution such as, “Is this the best solution of all the possibilities?” or “Is this the right material choice?” or “Am I correct in assuming that this can be treated in this simplified fashion?”

Being skeptical of our own thoughts and that of others is another common characteristic. We are proud of ourselves when we see our own ingenuity and analytic skills improve something or shape something properly or solve a forensic problem.  Mistakes will still reveal themselves in projects, but engineering is not about that past, it is about taking action now and bringing the project to a lower state of imperfection. Experience is necessary to be able to see a few good potential solutions to a problem within an infinite amount of options.  Our intuition is strengthened every year of our careers. Since problems in engineering are rarely simple or straightforward, it takes a high level of self-reflection and intuition to tackle them.